Distribution enhanced polyolefin meltspinning process and product

Abstract

Improved meltspinning productivity is achieved by employing polyolefin resins having key molecular weight distribution and rheological property parameters within predetermined ranges. These parameters include the molecular weight distribution breadth parameter, Mz/Mn; and rheological property parameters of flow rate ratio, I10/I2, and the power law index, n, of the regression analysis viscosity equation. These parameters additionally include one or both of the z-average molecular weight, Mz, of the resin, or the second order constant, b2, of the regression analysis viscosity equation, and unless both of the latter two parameters are met, the parameters further include the die swell and the spinnability factor (determined from the relationship between die swell and MFR) of the resin.

That which is claimed is: 
     
       1. An enhanced productivity meltspinning process for meltspinning polyolefin filaments comprising: extruding molten polyolefin through a plurality of filament forming orifices to form a plurality of filaments, quenching said filaments and subjecting said quenched filaments to an attenuation force, wherein the polyolefin resin supplied to the filament forming orifices is an enhanced molecular weight distribution polyolefin resin having property parameters comprising; (i) a molecular weight distribution breadth, M z  /M n , of between 7.2 and 10, a flow rate ratio of less than 15.5, and a power law index at 20 sec -1  of between 0.70 and 0.78; and   (ii) either a z-average molecular weight, M z , of between 400,000 and 580,000, or a second order constant, b 2 , determined from the regression analysis viscosity equation, of between -0.029 and -0.047, or both; and   (iii) unless both of the M z  and b 2  parameters is within said ranges of between 400,000 and 580,000, and between -0.029 and -0.047, respectively, a die swell, B 2 , of between 1.6 and 2.0, and a spinnability factor ln(B 2 )/MFR of between about 0.08 and about 0.026.     
     
     
       2. The meltspinning process of claim 1 wherein said polyolefin resin of enhanced molecular weight distribution comprises a calculated viscosity at 230° C. and a shear rate of 20 s -1  of less than about 4350 poise. 
     
     
       3. The meltspinning process of claim 1 wherein said polyolefin resin of enhanced molecular weight distribution comprises a melt flow rate determined according to ASTM D-1238-82, condition 230/2.16, of between 15 and 70. 
     
     
       4. The meltspinning process of claim 1 wherein said polyolefin resin of enhanced molecular weight distribution comprises a flow rate ratio of less than or equal to 15.30. 
     
     
       5. The meltspinning process of claim 1 wherein said polyolefin resin of enhanced molecular weight distribution comprises a z-average molecular weight, M z , of between 400,000 and 480,000. 
     
     
       6. The meltspinning process of claim 1 wherein said polyolefin resin of enhanced molecular weight distribution comprises a spinnability factor ln(B 2 )/MFR of between about 0.012 and about 0.019. 
     
     
       7. The meltspinning process of claim 1 wherein the attenuation force applied to said quenched polyolefin filaments is applied by a filament winding apparatus. 
     
     
       8. The meltspinning process of claim 1 wherein said attenuation force applied to said quenched polyolefin filaments is applied by a pneumatic drawdown system. 
     
     
       9. The meltspinning process of claim 8 wherein the pneumatic drawdown system comprises a plurality of air aspirator guns. 
     
     
       10. The meltspinning process of claim 8 wherein the pneumatic drawdown system is a slot draw attenuation zone. 
     
     
       11. The meltspinning process of claim 8 wherein the quenched filaments achieve a velocity of between about 500 meters/minute up to about 5000 meters/minute during said meltspinning process. 
     
     
       12. The meltspinning process of claim 11 wherein said quenched polyolefin filaments achieve a velocity of greater than about 2000 meters/minute during said meltspinning process. 
     
     
       13. The meltspinning process of claim 11 additionally comprising the steps of depositing said filaments on a moving screen to form a spunbonded fabric. 
     
     
       14. An enhanced productivity meltspinning process for meltspinning polypropylene filaments comprising: extruding molten polypropylene through a plurality of filament forming orifices to form a plurality of filaments, quenching said filaments and subjecting said quenched filaments to an attenuation force, wherein the polypropylene resin supplied to the filament forming orifices is an enhanced molecular weight distribution polypropylene resin having property parameters comprising; (i) a molecular weight distribution breadth, M z  /M n , of between 7.2 and 10, a flow rate ratio of less than 15.5, and a power law index at 20 sec -1  of between 0.70 and 0.78; and   (ii) either a z-average molecular weight, M z , of between 400,000 and 580,000, or a second order constant, b 2 , determined from the regression analysis viscosity equation, of between -0.029 and -0.047, or both; and   (iii) unless both of the M z  and b 2  parameters is within said ranges of between 400,000 and 580,000, and between -0.029 and -0.047, respectively, a die swell, B 2 , of between 1.6 and 2.0, and a spinnability factor ln(B 2 )/MFR of between about 0.08 and about 0.026.     
     
     
       15. The meltspinning process of claim 14 wherein said polypropylene resin of enhanced molecular weight distribution comprises a melt flow rate determined according to ASTM D-1238-82, condition 230/2.16, of between 15 and 70. 
     
     
       16. The meltspinning process of claim 14 wherein said polypropylene resin of enhanced molecular weight distribution comprises a flow rate ratio of less than or equal to 15.30. 
     
     
       17. The meltspinning process of claim 14 wherein said polypropylene resin of enhanced molecular weight distribution comprises a z-average molecular weight, M z , of between 400,000 and 480,000. 
     
     
       18. The meltspinning process of claim 14 wherein said polypropylene resin of enhanced molecular weight distribution comprises a spinnability factor ln(B 2 )/MFR of between about 0.012 and about 0.019. 
     
     
       19. The meltspinning process of claim 14 wherein said polypropylene resin of enhanced molecular weight distribution comprises both a z-average molecular weight, M z , of between 400,000 and 580,000, and a second order constant, b 2 , determined from the regression analysis viscosity equation, of between -0.029 and -0.047. 
     
     
       20. The meltspinning process of claim 14 wherein said attenuation force applied to said quenched polypropylene filaments is applied by a pneumatic drawdown system. 
     
     
       21. The meltspinning process of claim 20 wherein the pneumatic drawdown system comprises a plurality of air aspirator guns. 
     
     
       22. The meltspinning process of claim 20 wherein the pneumatic drawdown system is a slot draw attenuation zone. 
     
     
       23. The meltspinning process of claim 22 wherein the quenched filaments achieve a velocity of between about 500 meters/minute up to about 5000 meters/minute during said meltspinning process. 
     
     
       24. The meltspinning process of claim 22 additionally comprising the steps of depositing said filaments on a moving screen to form a spunbonded fabric. 
     
     
       25. The meltspinning process of claim 14 wherein said polypropylene resin of enhanced molecular weight distribution primarily comprises a polypropylene copolymer or terpolymer resin. 
     
     
       26. An enhanced productivity meltspinning process for meltspinning polypropylene filaments comprising: extruding molten polypropylene through a plurality of filament forming orifices to form a plurality of filaments, quenching said filaments and subjecting said quenched filaments to an attenuation force, wherein the polypropylene resin supplied to the filament forming orifices is an enhanced molecular weight distribution polypropylene resin having property parameters comprising;   a molecular weight distribution breadth, M z  /M n , of between 7.2 and 10, a flow rate ratio of less than 15.5, and a power law index at 20 sec -1  of between 0.70 and 0.78, a z-average molecular weight, M z , of between 400,000 and 580,000, a second order constant, b 2 , determined from the regression analysis viscosity equation, of between -0.029 and -0.047, a die swell, B 2 , of between 1.6 and 2.0, and a spinnability factor ln(B 2 )/MFR of between about 0.08 and about 0.026.   
     
     
       27. The meltspinning process of claim 26 wherein said polypropylene resin of enhanced molecular weight distribution comprises a melt flow rate determined according to ASTM D-1238-82, condition 230/2.16, of between 15 and 70. 
     
     
       28. The meltspinning process of claim 26 wherein said polypropylene resin of enhanced molecular weight distribution comprises a flow rate ratio of less than or equal to 15.30. 
     
     
       29. The meltspinning process of claim 26 wherein said polypropylene resin of enhanced molecular weight distribution comprises a z-average molecular weight, M z , of between 400,000 and 480,000. 
     
     
       30. The meltspinning process of claim 26 wherein said polypropylene resin of enhanced molecular weight distribution comprises a spinnability factor ln(B 2 )/MFR of between about 0.012 and about 0.019. 
     
     
       31. The meltspinning process of claim 26 wherein said attenuation force applied to said quenched polypropylene filaments is applied by a pneumatic drawdown system. 
     
     
       32. The meltspinning process of claim 31 wherein the pneumatic drawdown system comprises a plurality of air aspirator guns. 
     
     
       33. The meltspinning process of claim 32 wherein the pneumatic drawdown system is a slot draw attenuation zone. 
     
     
       34. The meltspinning process of claim 33 wherein the quenched filaments achieve a velocity of between about 500 meters/minute up to about 5000 meters/minute during said meltspinning process. 
     
     
       35. The meltspinning process of claim 34 additionally comprising the steps of depositing said filaments on a moving screen to form a spunbonded fabric.